Deposition apparatus

ABSTRACT

Means feed wire to be evaporated into contact with a central portion of an evaporator-filament having an electric current passing therethrough. An electrical potential difference is maintained between the wire and one side of said filament whereby the vapor is ionized.

121Q 121/I 55H 1 132912-1172 KR he m/291 United States Patent Judd eta1. Sept. 12, 1972 [54] DEPOSITION APPARATUS [56] References Cited [72]Inventors: Joseph H. Judd, Newport News; UNITED STATES PATENTS a ClarkHampton both 2,153,786 4/1939 Alexander etal ..ll8/49 x 2,444,763 7/1948Alexander ..ll8/49 x [73] Assignee: The United States of Ameri a3,045,642 7/1962 Auzolle eta] ..118/49 zfig fffizfg g gmmg g g FOREIGNPATENTS OR APPLICATIONS Administration 55,291 10/1943 Netherlands..118/49 [22] Filed: April 1971 Primary Examiner-Morris Kaplan [21]App1.N0.: 138,229 Att0rneyHoward J. Osborn, William H. King and John R.Manning [521 US. Cl. ..l18/49.1, 204/298, mag/ 192,12 1; [57] ABSTRACT51 Int. (:1 ..C23c 13/12 Means feed wire to be evaporated into Contact wa 58 Field at Search ..118/48-49.1; central Portion of an evaporator-WWWhaving electric current passing therethrough. An electrical potentialdifference is maintained between the wire 204/298 and one side of saidfilament whereby the vapor is ionized.

4 Claims, 2 Drawing Figures l8 I l3 9 POVbER 5 20 I2 1 I POWER SUPPLY 1SUPPLY 2 POWER 3 24 SUPPLY M PATENTEDSEP 12 I972 3,690,291

sum 1 or 2 l4 7 i 2 22 |e l3 1 2o 1 POWER I I POWER SUPPLY I SUPPLY 23POWER 24 v SUPPLY FIG l INVENTORS JOSEPH H. JUDD RAYMOND L. CLARKPATENTED E 2 3.690.291

sum 2 OF 2 FIG. 2

INVENTORS JOSEPH H. JUDD BYwD lfiLARK ATTORN S DEPOSITION APPARATUSORIGIN OF THE INVENTION The invention described herein was made byemployees of the United States Government and may be manufactured andused by or for the Government for governmental purposes without thepayment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The invention relates generally to materialcoating and more specifically concerns depositing a thin metallic filmon nonmetallic materials.

In the past, vapor deposition techniques have been used wherein acoating material is vaporized by heat in a vacuum and'then condenses onthe material to be coated. The primary disadvantages of these techniquesin coating nonmetallic substrates with metallic films is that there isno adhesion between the metallic film and the nonmetallic substrate.Also, there is very little control of the coating thickness in thesetechniques.

Other techniques used in the past consists of the cold cathodegeneration of the metal vapor. The disadvantage of thistechnique is thatit cannot be controlled either by electric potential or by anodegeometry to supply a uniform metal vapor. The almost instantaneousconsumption of the cathode in the cold cathode technique results in thegeneration of a mixture of metal droplets and vapor which producesunsatisfactory thin metallic films. Under microscopic examination, thefilms are found to be uneven and the condensed metal droplets areevident in the thicknesses of 100 to 500 angstroms.

It is therefore the primary purpose of this invention to provideapparatus for applying thin metallic films to nonmetallic materials inwhich the film thicknesses are even and in which adhesion exists betweenthe metallic film and the nonmetallic materials.

SUMMARY OF THE INVENTION The invention includes a tungsten filament, apositive plate, a negative plate, and an electric motor located inside avacuum bell jar. The tungsten fiIament, electric motor, and positive andnegative plates are supplied by power supplies located outside the belljar. Specimens of the nonmetallic material that are to be coated areattached to both the positive and the negative plates. The electricmotor feeds the coating material into the tungsten filament so that itmakes contact with the tungsten filament at about its central portion.As the coating material is being fed into the tungsten filament, it iselectrically connected to one side of the filament. Hence, there is avoltage difference between the coating material and the central portionof the tungsten filament. As the coating material is fed into thetungsten filament, it is vaporized by the heat from the filament and atthe same time due to the potential difference between the end of thecoating material andthe central position of the filament a currentexists. This results in a very fine ionized vapor of the coatingmaterial which is attracted to both the negative and the positive platesthereby coating the attached specimen.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of anembodiment of this invention; and

FIG. 2 is a schematic drawing of the mechanism for feeding the coatingmaterial into the filament.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the embodiment ofthe invention selected for illustration in the drawings, the number 11designates a vacuum bell jar. Inasmuch as the equip ment for theevacuation bell jars is well known the details of this equipment are notdisclosed in the drawings. Located inside bell jar 11 is a tungstenfilament 12 which is connected across a power supply 13 located outsidethe bell jar. Two places, 14 and 15, located inside the bell jar areconnected to a power supply 15 outside the bell jar such that plate 14is a negative plate and plate 15 is a positive plate. An electric motor17 located in the bell jar is powered by a power supply 18 to feed thecoating material 19 into the central portion of tungsten filament 12.The coating material 19 is fed into filament 12 by a feed mechanism 20.The details of feed mechanism 20 are disclosed in FIG. 2. The lowerportion of filament 12 is connected through feed mechanism 20 to coatingmaterial 19 thereby creating a potential difference between the end ofthe coating material 19 and the central portion of the tungsten filament12. A specimen 21 of the material to be coated is attached to plate 14by a metal clip 22 and a specimen 23 of the material to be coated isattached to plate 15 by a metal clip 24. In addition to attaching thespecimen to plates 14 and 15, metal clips 22 and 24 dissipate anyelectric charge that might be formed on the face of the specimen.

The feed mechanism in FIG. 2 includes a teflon or nylon adapter 25 whichis coupled to the output shaft 26 of motor 17 such that adapter 25rotates as shaft 26 rotates. A hole 27 in adapter 25 allows a shaft 28to move longitudinally in the hole. Two slots 29 and 30 are in adapter25 and a key 31 extends through shaft 28 into slots 29 and 30. Henceshaft 28 rotates with adapter 25 and is free to move longitudinally withrespect to the adapter. A support 32 is attached to motor 17forsupprting a metal block 33. Shaft 28 has threads 34 which engage withfemale threads that extend through block 33. The end of shaft 28 has achuck 35 attached to it. Chuck 35 holds the rod of plating material 19that is fed into filament 12. Rod 19 is held off-center of shuck 35 sothat rod 19 engages filament 12 once every revolution of the chuck. Awire 36 has one of its ends connected to block 33 and its other endconnected to the bottom of filament 12. Hence there is a potentialdifference between the unattached end of rod 19 and the central portionof filament 12. In the operation of the feed mechanism, when motor 17turns shaft 26, adapter 25 turns which turns shaft 28 causing it tothread through block 33. This causes chuck 35 to rotate and move awayfrom block 33. Hence, with every revolution of chuch 35, rod 19 makescontact with filament 12. The length of rod 19 that makes contact withfilament 12 is the distance that chuck 35 moves longitudinally duringone revolution. To produce la a higher ratio of time with the anode notin contact with the filament to the time with the anode in contact, atime delay during motor rotation is introduced; in tests of theapparatus a mechanical brake on the motor was used.

The embodiment of the invention disclosed in the drawings has been usedto obtain excellent metallic coatings on elastomers by applying thefollowing procedure. Samples are cleaned to remove dust and film andthen attached to both positive and negative plates 14 and 15 by metalclips 22 and 24. The vacuum system is then closed and pumped down to thetorr range. Dry argon is used to backfill the system and a flowdischarge is made in the chamber for corona scrubbing. Then the vacuumsystem is again evacuated and an electric potential is applied acrossthe positive and negative plates. The tungsten filament is heated to themelting point of the rod and the rod is driven by the electric motorinto the tungsten filament. For very thin metallic films, one revolutionof chuck 35 is sufficient.

The advantage of this invention is that it provides the ability toproduce metallic coatings with good adhesions on a wide range ofnonmetallic materials that were impractical or impossible to coat byprevious processes.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a preferred embodiment. Various changes maybe made in the shape, size and arrangement of parts. For example,equivalent elements may be substituted for those illustrated anddescribed herein, parts may be reversed, and certain features of theinvention may be utilized independently of the use of other features allwithout departing from the spirit or scope of the invention as definedin the subjoined claims. Means other than electric motor 17 could beused to feed rod 19 of the coating material into the central portion oftungsten filament 12. Also, means other than what is shown could be usedto create a potential difference between the end of rod 19 and thecentral portion of tungsten filament 12.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. Apparatus for depositing a coating of metallic material on anonmetallic substrate comprising: a plate with an electric potentialapplied to it and with the substrate attached to it; an electricallyheated filament; a rod of the coating material electrically connected toone side of said filament; and means for striking said rod against thecentral portion of said filament to form a very fine ionized vapor ofsaid coating material whereby said vapor is attracted by said plate anddeposited on said substrate.

2. Apparatus according to claim 1 with two plates instead of one andwith a positive potential applied to one plate and a negative potentialapplied to the other plate.

3. Apparatus according to claim 1 wherein said means for striking saidrod against the central portion of said filament includes rotating meansfor holding said rod off-center of rotation of said rotating means; andmeans for moving said rotating means in the direction of the centralportion of said filament while said rotating means is rotating wherebyduring each revolution of said rotating means said rod is wiped acrossthe central portion of said filament.

4. Apparatus according to claim 3 wherein said means for moving saidrotating means in the direction of the central portion of said filamentincludes a motor that rotates a threaded shaft that has said holdingmeans attached to its end.

1. Apparatus for depositing a coating of metallic material on anonmetallic substrate comprising: a plate with an electric potentialapplied to it and with the substrate attached to it; an electricallyheated filament; a rod of the coating material electrically connected toone side of said filament; and means for striking said rod against thecentral portion of said filament to form a very fine ionized vapor ofsaid coating material whereby said vapor is attracted by said plate anddeposited on said substrate.
 2. Apparatus according to claim 1 with twoplates instead of one and with a positive potential applied to one plateand a negative potential applied to the other plate.
 3. Apparatusaccording to claim 1 wherein said means for striking said rod againstthe central portion of said filament includes rotating means for holdingsaid rod off-center of rotation of said rotating means; and means formoving said rotating means in the direction of the central portion ofsaid filament while said rotating means is rotating whereby during eachrevolution of said rotating means said rod is wiped across the centralportion of said filament.
 4. Apparatus according to claim 3 wherein saidmeans for moving said rotating means in the direction of the centralportion of said filament includes a motor that rotates a threaded shaftthat has said holding means attached to its end.